When comparing Instagram Direct vs Signal, the Slant community recommends Signal for most people. In the question“What are the best messaging apps for Android?”Signal is ranked 3rd while Instagram Direct is ranked 32nd. The most important reason people chose Signal is:

Signal uses an advanced end to end encryption protocol that provides privacy for every message every time.

Pros

Pro

Video & photo messages

Pro

Filters

Pro

Group messages

With up to 15 people.

Pro

Provides security and privacy

Signal uses an advanced end to end encryption protocol that provides privacy for every message every time.

Pro

Free and open source

Signal is free and open source software, enabling anyone to verify its security by auditing the code. It's the only private messenger that uses open source, peer-reviewed cryptographic protocols to keep your messages safe.

Pro

SMS/MMS support

Signal can be your default SMS/MMS text messenger. Encryption is not possible when sending SMS to your contacts, however.

Pro

Recommended by Edward Snowden

Edward Snowden uses this messenger and recommends it to everony who is concerned about his privacy.

Supports sharing of various different media types

Pro

Supports encrypted group chats

Pro

You can easily view all media exchanged

You can easily view all media shared in the chat without scrolling back to when it was shared.

Pro

Message mirroring on Signal Desktop

Signal Desktop is a Chrome extension that allows you to mirror messages from your phone, including replying.

Cons

Con

Walled garden

Can't communicate with people outside of Instagram.

Con

Single device

You cannot send and receive messages from multiple devices.

Con

If SMS/MMS imported, other apps can't read SMS

For those using Join, Pushbullet, or similar apps to send and receive SMS/MMS from web or desktop, putting your SMS in Signal somehow breaks this functionally. The dev is aware but plans to remedy the situation have not been named a priority

Con

Uses message mirroring

You phone must be on and connected to the internet for Signal Desktop to work.